(a) Field of the Invention
The present invention relates to a binocular stereo-microscope.
(b) Description of the Prior Art
Generally, optical axes of objectives of a binocular stereo-microscope are vertical in order to enable the observation of an object placed horizontally. However, in a formation wherein eyepieces are arranged directly on those optical axes of objectives, a long observation causes fatigue to the observer since he has to look vertically into the eyepieces. Therefore, optical axes are deflected as described below in order to facilitate observation. Hereinafter, the description is given based on one of the right and left optical systems constituting the binocular stereo-microscope. That is, as shown in FIG. 1, the optical axis O.sub.1 of the objective 1 is made inclined by disposing an optical axis deflection prism 2 and an eyepiece 4 to enable an observer to look into the eyepiece 4 only by slightly declining his head downwards. Further, as it is necessary to enable a "stereo" observation, it is not favorable that an inverted image is observed as in ordinary microscopes. Therefore, a conventional binocular stereo-microscope has a Porro prism 3 arranged before the eyepiece 4 on the inclined optical axis O.sub.2 to erect the image so that an object can be observed exactly the same as its real form in both vertical and horizontal directions. However, such formation needs two kinds of prisms which are not economical and increase the size and weight of the eyepiece portion.